A mobile communication system means a system by which an operator provides communication services for a user terminal (e.g., a mobile phone) by deploying a wireless access network device (e.g., a base station), a core network device (e.g., a Home Location Register, HLR), etc. It is mainly applied to a licensed frequency band for the operator to obtain a license through auction, distribution or the like and to use a specific spectrum resource for network deployment. Mobile communication has experienced the first, second, third and fourth generations. The first generation of mobile communication means an original analog voice-only cellular phone standard, mainly using the analog technology and the Frequency Division Multiple Access (FDMA) method. The second generation of mobile communication introduces the digital technology to improve the network capacity, the voice quality and confidentiality, represented by Global System for Mobile Communication (GSM) and Code Division Multiple Access (CDMA IS-95). The third generation of mobile communication mainly means three technologies of CDMA2000, WCDMA and TD-SCDMA, all of which are based on the code division multiple access. The fourth generation of mobile communication has relatively internationally unified standards, is Long Term Evolution/Long Term Evolution-Advanced (LTE/LTE-A) established by 3GPP (the 3rd Generation Partnership Project) of International Organization for Standardization, has a downlink based on Orthogonal Frequency Division Multiple Access (OFDMA) and an uplink based on Single Carrier-Frequency Division Multiple Access (SC-FDMA), and achieves high-speed transmission with a downlink peak value of 1 Gbps and an uplink peak value of 500 Mbps based on a flexible bandwidth and a self-adaptive modulation and coding mode.
However, wireless communication, for example, WiFi, on an unlicensed frequency band is a general term for the 802.11-series technologies developed by the Institute of Electrical and Electronics Engineers IEEE, for example, 802.11a/g/n/ac. WiFi is mainly applied to local wireless communication, generally has a relatively smaller coverage, and is a simple and relatively cheaper wireless communication means. WiFi of the original version works at 2.4 GHz, but a relatively smaller available bandwidth in the 2.4 GHz frequency band and more wireless transmitting devices working in the 2.4 GHz frequency band result in a decline of performance of WiFi working at 2.4 GHz. A new communication frequency of 5 GHz (note: 5 GHz described herein does not mean a single frequency point but various frequency bands around 5 GHz and can be understood as frequency bands from 5.1 GHz to 5.9 GHz) has been explored for WiFi of later versions. In order to solve a contradiction between the increasing demand for data traffic and the increasingly scarce radio frequency, recently, 3GPP has begun their studies on application of an LTE system to the unlicensed frequency band, aiming to increase the available bandwidth for the LTE system. The Licensed Assisted Access (LAA) currently discussed in 3GPP mainly aggregates licensed and unlicensed frequency bands by Carrier Aggregation (CA), and extends the LTE system to the unlicensed frequency band for transmission. In Rel.13 standards, using the unlicensed frequency band for downlink transmission and introducing the Listen Before Talk (LBT) mechanism have been standardized.
In the Rel. 14 version of 3GPP, the unlicensed frequency band is used for uplink transmission, and an uplink LBT method is being studied. Meanwhile, the MulteFireAlliance, which introduces LTE into the unlicensed frequency band in standalone mode, is also studying the uplink LBT method.
In an uplink transmission process, a User Equipment (UE) needs to perform LBT before uplink transmission. Uplink transmission cannot be performed until successful LBT. However, if an uplink scheduled UE (i.e., UE1 in FIG. 1) of the nth subframe is transmitting data when an uplink scheduled UE (i.e., UE2 in FIG. 1) of the (n+1)th subframe performs LBT before transmitting data, the uplink scheduled UE of the (n+1)th subframe may be interfered. Thus, LBT of the uplink scheduled UE of the (n+1)th subframe fails, and the data cannot be transmitted. For details, refer to FIG. 1.
In order to avoid the phenomenon that the LBT of the uplink scheduled UE of the (n+1)th subframe fails because the uplink scheduled UE of the (n+1)th subframe is interfered by the uplink scheduled UE that transmits data on the nth subframe and the (n+1)th subframe. The following two solutions are mainly provided in the prior art.
The first solution: referring to FIG. 2, the uplink scheduled UE (i.e., UE1 in the figure) that transmits data on the nth subframe and the (n+1)th subframe applies puncturing in data of a time period of one or more symbols at a beginning portion of the (n+1)th subframe; a new uplink scheduled UE (i.e., UE2 in the figure) of the (n+1)th subframe uses this time period to perform LBT; and after the new uplink scheduled UE of the (n+1)th subframe successfully performs LBT, data transmission is performed. A vertical line in FIG. 2 is a subframe boundary of the nth subframe and the (n+1)th subframe.
The second solution: referring to FIG. 3, an uplink scheduled UE (i.e., UE1 in the figure) that transmits data on the nth subframe and the (n+1)th subframe applies puncturing on data of a time period of one or more symbols at an ending portion of the nth subframe; a new uplink scheduled UE (i.e., UE2 in the figure) of the (n+1)th subframe uses this time period to perform LBT; and after the new uplink scheduled UE of the (n+1)th subframe successfully performs LBT, data transmission is performed.
However, in the existing solutions (i.e., the first solution and the second solution described above), a UE that performs transmission (i.e., the uplink scheduled UE that transmits data in the nth subframe and the (n+1)th subframe) will pause data transmission. Consequently, the system overhead is increased and the uplink transmission data rate is reduced. Besides, as the UE needs to pause data transmission, other systems may take up a channel, resulting in LBT failures and reducing the channel occupancy probability.
Currently, no effective solution has been proposed to solve the above problem.